October 17, 2012

Ancient mtDNA haplogroup X2 from Central Europe

Davidski reminds me of a paper by Lee et al. I had posted the abstract of, but did not comment on. He highlights the fact that mtDNA haplogroup X2 has been detected at this site (3.6-2.8ky cal BC) but not in earlier LBK Neolithic Europeans. Furthermore, he attributes the arrival of X2 in Europe to "Northwest Eurasians":

Reading the quotes below, I can’t help thinking that X2 lineages in Europe might be associated with the arrival of the so called Northwest Eurasians of North/Central/East Europe and the North Caucasus, while X1 with the earlier migrations of the Sardinian-like Southwest Eurasians of Mediterranean Europe, North Africa and the Near East.

However, mtDNA haplogroup X2 seems to have originated in the Near East:

Finally, phylogeography of the subclades of haplogroup X suggests that the Near East is the likely geographical source for the spread of subhaplogroup X2, and the associated population dispersal occurred around, or after, the LGM when the climate ameliorated. The presence of a daughter clade in northern Native Americans testifies to the range of this population expansion.

Moreover, it occurs at a higher frequency in Southern Europeans than Northern Europeans and is well-represented in the Caucasus, Near East, and even Africa. These twin facts are inconsistent with it being related to "Northwest Eurasians", however that hypothetical people is defined.

Of related interest, mtDNA haplogroup X2b has been detected in Iron Age "princely burials" from the same location and by the same group. Also from Reidla et al.:

The sister groups X2b and X2c (X1 and X2, respectively, in the work of Herrnstadt et al. 2002) encompass one-third of the European sequences (excluding the samples from the North Caucasus). It is of interest that some North African sequences (from Morocco and Algeria) belong to X2b as well. Subhaplogroup X2b shows a diversity that is consistent with a postglacial population expansion in both West Eurasia and North Africa.

Fernandes et al. (2012) consider X2b to be of European origin. X2 has been discovered in a Megalithic long mound from France (4.2ky cal BP), and in abundance at Treilles (c. 3,000 BC), in the latter case associated with a predominantly Y-haplogroup G2a (with some I-P37.2) population. In Jean Manco's excellent compendium, X2b is also listed as being present in Neolithic Portugal (3,400 years BC), and X2j in Neolithic Germany (4625-4250 BC); the latter is said to be "North African" by Fernandes et al. (2012).

Therefore, we can probably reject Davidski's speculation...

So, X2 has been located at multiple late Neolithic sites in Central Europe, including the Corded Ware burial ground at Eulau, Eastern Germany. Of course, that’s also where Y-chromosome haplogroup R1a was found (see here). I suspect this wasn’t a coincidence and it’s likely these markers entered Europe together from the east, probably between 4,000 and 3,000 B.C.

X2 shows no association with northern Europeans at present, and occurs in ancient DNA samples from Western Europe that show no indication of being related to Y-haplogroup R1a at all, and even precede the hypothetical 4-3ky BC entry window.

Also of interest is that no X2 was mentioned in recent published data from Ukraine and West Siberia, and none of it was detected in Mesolithic Europeans. So, it seems that X2 variants entered Europe during the Neolithic, and there is no indication that they did so with Davidski's hypothetical R1a-bearing Northwest Europeans.

8 comments:

To me it seems plausible X2 and X1 are more related to early Anatolians (maybe as hunter-gatherers) who may have been in the Caucasus, but also moved into the ancient Near East. Consider the Druze who have various distinct mutations for these X1/X2 lineages. From the data so far, a Neolithic immigration to Europe is plausible, but so far nothing can be ruled out. Even some mesolithic European lineages (ie: U4) are present in the Near East from Jean M's compendium. I think it's clear there is overlap and we really need a FGS where possible for the lowest level of granularity.

Although Family Tree DNA lists my mtDNA classification as "projected W1e" (pending further testing), my DNA is kind of unusual because it contains the signature motifs of both X and W... And according to the latest analysis on James Lick's "mitohap" site, it is probably >> X2m1 << now. The original certificate from Genographic says "X".

Both the Northwest Eurasians and Southwest Eurasians came from the Near East. The former entered Europe from the east, while the latter from North Africa and the Mediterranean.

The Northwest Eurasians carried a variety of markers, which included R1a and X2 (in fact, I suspect it's X2e that I'm talking about), and very little or no X1. On the other hand, the Southwest Eurasians carried clear amounts of X1.

The fact that the Southwest Eurasians probably also carried X2 (X2b?) isn't relevant.

I'm only using these mtDNA lineages to track their movements. It makes no difference that X2 is today more common in Southern Europe, because I'm not claiming that X2 was an substantial part of the Northwest Eurasian mtDNA makeup. But it certainly looks like a very nice signal of their initial movements into Europe.

If we say that there were two related but fairly distinct Neolithic waves into Europe, one from the south and southwest, and the other from the east, and the latter mixed significantly with Mesolithic Europeans, then everything makes sense.

The recent discovery, via ancient DNA and rolloff, that mixing between these different groups took thousands of years in Europe makes this even more plausible.

The Northwest Eurasians carried a variety of markers, which included R1a and X2 (in fact, I suspect it's X2e that I'm talking about), and very little or no X1. On the other hand, the Southwest Eurasians carried clear amounts of X1.

From Reidla et al.

"Clades X2e and X2f encompass the majority (87.1%) of the sequences from the South Caucasus area and show coalescence times (12,000 ± 4,000 YBP and 10,800 ± 5,000 YBP, respectively) consistent with a Late Upper Paleolithic (LUP) origin and a subsequent spread in the region. We found significant differences between the haplogroup distribution between the North and the South Caucasian samples, a result that indicates a major geographical barrier between the two regions. The South Caucasian sample is enriched in mtDNAs belonging to clades X2e and X2f (P less than .01), whereas the North Caucasian sample shows a higher proportion of sequences derived at nps 225 and 16248 (P less than .01)."

It is good to see that you are coming around to the fact that Europe received gene flow from the South Caucasus in the 4-3ky BC timeframe, which is precisely the date inferred by rolloff for a major European-West Asia admixture in Ukrainians and Lithuanians.

I just said that the Northwest Eurasians originally came from the Near East. Obviously, the Near East is south of the Caucasus. So my claims that X2, and more specifically X2e, is a signal of their entry into Central Europe seems fine.

And I don't know what rolloff experiment you're referring to, but all those I've seen here and elsewhere show a West Asian-North European admixture event way past the 4-3ky BC timeframe. But this is actually in line with a 4-3ky BC entry of the Northwest Eurasians into Central Europe, followed by slow mixing.

Of course, you do realize that the Northwest Eurasians are most likely the people who carried the so called West Asian admixture signal into Europe, right? So this doesn't bode well for your J2 + West Asian Bronze Age Indo-European invasion of Europe.

More like it, it was just a movement of R1a West Asians into a relatively empty Central Europe during the late Neolithic, followed by slow mixing with the remnants of earlier Neolithic groups plus Mesolithic survivors. No wonder then, that Oetzi types were still alive all over Southern Europe well into the metal ages.

Of course, you do realize that the Northwest Eurasians are most likely the people who carried the so called West Asian admixture signal into Europe, right?

No, I don't realize that. West_Asian shows no evidence of being "Northwest Eurasian". I have already showed in my Orcadian/Lithuanian analysis that segments that appear West_Asian tend to be "Near_East" rather than "Atlantic_Baltic" in a bipartite scheme. So, if by "Northwest Eurasian" you mean segments that are more like Saudis than Poles, then your terminology needs a little grooming.

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